Electrostatic fluidized bed coating is now a conventional and widely-used technique for depositing particulate materials upon a great diversity of workpieces. In Knudsen United States Pat. No. 3,916,826, apparatus is described in which ionized air is employed for the simultaneous charging and fluidization of the particulate coating material employed therein, affording the advantage of safety, combined with outstanding effectiveness. An important prerequisite to satisfactory operation of such apparatus is the efficient ionization of the air so employed. While the various high-efficiency charging means described by Knudsen are entirely effective and satisfactory, even more efficient ionization of the air would produce concomitantly better results, with less power consumption, and hence with greater safety and at lower cost. Moreover, alternative electrode configurations and air flow patterns may be desired for some purposes.
Accordingly, it is an object of the present invention to provide a novel electrostatic fluidized bed coating method wherein air used to fluidize and charge the coating material is ionized in a highly efficient and effective manner.
It is also an object of the invention to provide such method wherein operation occurs at reduced levels of power consumption and, therefore, with improved safety and lower cost.